In response to an ACTIVATE PACKET DATA PROTOCOL (PDP) CONTEXT REQUEST message from a host, including a global reachability request option that requests a global IP address and a global port to be allocated to the host, a serving gateway transmits a CREATE PDP CONTEXT REQUEST message to an Internet gateway device. The CREATE PDP CONTEXT REQUEST message includes the global reachability request option. In response to a CREATE PDP CONTEXT RESPONSE message from the Internet gateway, where the CREATE PDP CONTEXT RESPONSE message includes a global reachability response option specifying therein a global IP address and a global port allocated to the host, the serving gateway transmits an ACTIVATE PDP CONTEXT ACCEPT message to the host, where the ACTIVATE PDP CONTEXT ACCEPT message includes the global reachability response option. As a result, the host does not need to establish a separate connection session to the Internet gateway device to acquire the same.